Precise age of Bangiomorpha pubescens dates the origin of eukaryotic photosynthesis
Abstract
Although the geological record indicates that eukaryotes evolved by 1.9–1.4 Ga, their early evolution is poorly resolved taxonomically and chronologically. The fossil red alga Bangiomorpha pubescens is the only recognized crown-group eukaryote older than ca. 0.8 Ga and marks the earliest known expression of extant forms of multicellularity and eukaryotic photosynthesis. Because it postdates the divergence between the red and green algae and the prior endosymbiotic event that gave rise to the chloroplast, B. pubescens is uniquely important for calibrating eukaryotic evolution. However, molecular clock estimates for the divergence between the red and green algae are highly variable, and some analyses estimate this split to be younger than the widely inferred but poorly constrained first appearance age of 1.2 Ga for B. pubescens. As a result, many molecular clock studies reject this fossil ex post facto. Here we present new Re-Os isotopic ages from sedimentary rocks that stratigraphically bracket the occurrence of B. pubescens in the Bylot Supergroup of Baffin Island and revise its first appearance to 1.047 +0.013/–0.017 Ga. This date is 150 m.y. younger than commonly held interpretations and permits more precise estimates of early eukaryotic evolution. Using cross-calibrated molecular clock analyses with the new fossil age, we calculate that photosynthesis within the Eukarya emerged ca. 1.25 Ga. This date for primary plastid endosymbiosis serves as a benchmark for interpreting the fossil record of early eukaryotes and evaluating their role in the Proterozoic biosphere.
Additional Information
© 2017 Geological Society of America. Manuscript received 17 August 2017; Revised manuscript received 26 October 2017; Manuscript accepted 27 October 2017. This research was supported by the Agouron Institute, as well as funding from the Geo-mapping for Energy and Minerals (GEM), GEM-2, Natural Sciences and Engineering Research Council of Canada, and Polar Continental Shelf Program. Gibson acknowledges funding from the Eric Mountjoy Legacy Fund (McGill University), Mountjoy Exchange Award (Geological Association of Canada), and a Graduate Student Research Grant (Geological Society of America). We thank E.J. Javaux, A.D. Rooney, and an anonymous reviewer for constructive comments.Attached Files
Supplemental Material - 2018030.pdf
Files
Name | Size | Download all |
---|---|---|
md5:6ad3ed1ea4fc2914a2a3fd4c3973f0a8
|
1.8 MB | Preview Download |
Additional details
- Eprint ID
- 83811
- DOI
- 10.1130/G39829.1
- Resolver ID
- CaltechAUTHORS:20171211-142219174
- Agouron Institute
- Geo-mapping for Energy and Minerals (GEM)
- GEM-2
- Natural Sciences and Engineering Research Council of Canada (NSERC)
- Polar Continental Shelf Program
- McGill University
- Geological Association of Canada
- Geological Society of America
- Created
-
2017-12-12Created from EPrint's datestamp field
- Updated
-
2021-11-15Created from EPrint's last_modified field